Public Facility Provision Through the Reuse of Vacant Spaces: Service Performance Losses and Optimization Under Siting Constraints—A Case Study of Embedded Sports Facilities in Hangzhou

As cities shift toward regenerating existing urban areas, the reuse of vacant spaces for public facility provision is becoming an important alternative to new construction. In China, embedded sports facilities exemplify this approach, using fragmented spaces beneath bridges, vacant factories, rooftops, and underused parks and green spaces to supplement neighborhood sports services at low space-acquisition costs. Yet rapid growth in facility numbers does not necessarily translate into better service performance: some facilities remain underused or poorly matched to demand. We argue that potential land cost savings often motivate the reuse of vacant spaces, but the siting constraints of facilities provided through this approach may incur efficiency and equity losses. Taking embedded sports facilities in Gongshu District, Hangzhou, as a case study, we compare an unconstrained scenario with one constrained to vacant spaces. With equal numbers of additional facilities, non-dominated sorting genetic algorithm II (NSGA-II) generates efficiency–equity Pareto fronts to identify service performance losses attributable to siting constraints. Spatial regression and random forest–Shapley additive explanations (SHAP) analysis examine spatial variation in these losses, followed by tests of construction sequencing and sport-type reassignment. The findings indicate that identifying suitable local conditions, prioritizing construction, and updating functional configurations can provide pathways for improving service performance in the reuse of vacant spaces.